- Influence of the size and geometry of the anion binding pocket of sugar-urea anion receptors on chiral recognition
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Three new chiral urea-type anion receptors were synthesized from aromatic diamines and 1-amino-1-deoxyglucose. The anion binding properties of these receptors were studied using chiral carboxylates derived from mandelic acid and three α-amino acids. We found that the size of the anion binding pocket played an important role in chiral recognition processes. The best results were obtained for 1,8-diaminoanthracene and α-amino acid anions.
- Hamankiewicz, Paulina,Granda, Jaros?aw M.,Jurczak, Janusz
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- HYDRATES OF ORGANIC COMPOUNDS - VIII. THE EFFECT OF CARBOXYLATE ANIONS ON THE FORMATION OF CLATHRATE HYDRATES OF TETRABUTYLAMMONIUM CARBOXYLATES.
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In this study, from the solid-liquid phase diagrams for 19 binary mixtures of tetrabutylammonium carboxylate-water, the effect of the shape and/or length of the alkyl group of a carboxylate anion on the stability (i. e. , melting point) and the crystal structure (i. e. , hydration number) of their clathrate hydrates has been systematically examined. These fundamental data would also offer a guiding principle, for example, for highly selective separation of a specific carboxylate anion from an aqueous solution containing several kinds of carboxylate anions by means of the formation of a mixed clathrate hydrate of tetrabutylammonium carboxylates.
- Nakayama,Torigata
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- Lanthanide Complexes Supported by a Trizinc Crown Ether as Catalysts for Alternating Copolymerization of Epoxide and CO2: Telomerization Controlled by Carboxylate Anions
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A new family of heterometallic catalysts based on trimetalated macrocyclic tris(salen) ligands and rare-earth metals was prepared and structurally characterized. The LaZn3 system containing anionic ligands such as acetate plays a critical role in catalyzing the alternating copolymerization of cyclohexene oxide (CHO) and CO2 with a high proportion of carbonate linkages. Among the lanthanide metals, the CeZn3 system exhibits high catalytic activity with a turnover frequency (TOF) of over 370 h?1. NMR analysis of the complex and end-group analysis of the polymer suggest that the acetate ligands are rapidly exchanged, not only among coordinated acetates, but also between coordinated acetates and added carboxylate anions. These unique properties make this the first example of telomerization for the copolymerization of CHO and CO2.
- Nagae, Haruki,Aoki, Ryota,Akutagawa, Shin-Nosuke,Kleemann, Julian,Tagawa, Risa,Schindler, Tobias,Choi, Gyeongshin,Spaniol, Thomas P.,Tsurugi, Hayato,Okuda, Jun,Mashima, Kazushi
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- A method for detecting water in organic solvents
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(Chemical Equation Presented) The potent dehydrating ability of difluoro(aryl)-λ3-iodanes is exploited to develop a convenient 19F-NMR-based aquametry method that is more sensitive than coulometric Karl Fischer titration. The key difluoro(aryl)-λ3- iodane reagents are synthesized readily from commercially available and inexpensive precursors.
- Sun, Haoran,Wang, Bijia,Dimagno, Stephen G.
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- An azophenol-based chromogenic anion sensor
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(equation presented) A new chromogenic azophenol-thiourea based anion sensor, 2, has been developed. This system allows for the selective colorimetric detection of F-, H2PO4-, and AcO-. Selectivity trends turned out to be dependent upon guest basicity and conformational complementarity between 2 and the guest.
- Lee, Dong Hoon,Lee, Kwan Hee,Hong, Jong-In
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- Chiral recognition of carboxylate anions by (R)-BiNoL-based macrocyclic receptors
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Three (R)-BINOL-based macrocyclic receptors obtained via double-amidation reaction were used for chiral recognition of four anions derived from α-hydroxy and α-amino acids. The structural factors of hosts and guests that affect chiral recognition processes were also investigated, indicating that the proper geometry of both receptor and guest molecules plays a crucial role in effective enantio-discrimination.
- Tyszka-Gumkowska, Agata,Pikus, Grzegorz,Jurczak, Janusz
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- Regio- And diastereoselective Pd-catalyzed aminochlorocyclization of allylic carbamates: scope, derivatization, and mechanism
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The regio- and diastereoselective synthesis of oxazolidinonesviaa Pd-catalyzed vicinal C-N/C-Cl bond-forming reaction from internal alkenes of allylic carbamates is reported. The oxazolidinones are obtained in yields of 44 to 95% with high to excellent diastereoselectivities (from 6?:?1 to >20?:?1 dr) from readily available precursors. This process is scalable, and the products are suitable for the synthesis of useful amino alcohols. A detailed theoretical and experimental mechanistic study was carried out to describe that the reaction proceeds through ananti-aminopalladation of the alkene followed by an oxidative C-Pd(ii) cleavage with retention of the carbon stereochemistry to yield the major diastereomer. The role of Cu(ii) in a C-Cl bond-forming mechanism step has also been proposed.
- Ariga, Elaine Miho,Carita Correra, Thiago,Matsushima, Jullyane Emi,McIndoe, J. Scott,Moreira Ribeiro, Francisco Wanderson,Omari, Isaac,Papa Spadafora, Bruna,Rodrigues, Alessandro,Soares, Priscila Machado Arruda,Vinhato, Elisangela,de Oliveira-Silva, Diogo
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supporting information
p. 5595 - 5606
(2021/07/02)
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- Acetate-catalyzed hydroboration of CO2 for the selective formation of methanol-equivalent products
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The present study details the use of the acetate anion, an inexpensive and robust anion, as a CO2 hydroboration catalyst for the selective formation, in most cases, of methanol-equivalent borane products. Thus, upon heating (90 °C, PhBr), tetrabutylammonium, sodium and potassium acetate (1, 2 and 3, respectively) effectively catalyze CO2 hydroboration by pinacolborane (pinB-H) to afford CO2 reduction products HOCOBpin (A), pinBOCH2OBpin (B) and methoxyborane (C). In most cases, high selectivity for product C with higher borane loading and longer reaction time with a TON of up to 970 was observed. The reduction catalysis remains efficient at low catalyst loading (down to 0.1 mol%) and may also be performed under solvent-free conditions using salt 1 as a catalyst, reflecting the excellent robustness and stability of the acetate anion. In control experiments, a 1/1 1/pinB-H mixture was found to react fast with CO2 at room temperature to produce formate species [pinB(O2CH)(OAc)][N(nBu)4] (5) through CO2 insertion into the B-H bond. DFT calculations were also performed to gain insight into the acetate-mediated CO2 hydroboration catalysis, which further supported the crucial role of acetate as a Lewis base in CO2 functionalization catalysis by pinB-H. The DFT-estimated mechanism is in line with experimental data and rationalizes the formation of the most thermodynamically stable reduction product C through acetate catalysis.
- Dagorne, Samuel,Dos Santos, Jo?o H. Z.,Jacques, Béatrice,López, Carlos Silva,Nieto Faza, Olalla,Schrekker, Henri S.,Sokolovicz, Yuri C. A.,Specklin, David
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p. 2407 - 2414
(2020/05/13)
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- Electrocatalytic Reduction of Dioxygen to Hydrogen Peroxide by a Molecular Manganese Complex with a Bipyridine-Containing Schiff Base Ligand
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The synthesis and electrocatalytic reduction of dioxygen by a molecular manganese(III) complex with a tetradentate dianionic bipyridine-based ligand is reported. Electrochemical characterization indicates a Nernstian dependence on the added proton source for the reduction of Mn(III) to Mn(II). The resultant species is competent for the reduction of dioxygen to H2O2 with 81 ± 4% Faradaic efficiency. Mechanistic studies suggest that the catalytically active species has been generated through the interaction of the added proton donor and the parent Mn complex, resulting in the protonation of a coordinated phenolate moiety following the single-electron reduction, generating a neutral species with a vacant coordination site at the metal center. As a consequence, the active catalyst has a pendent proton source in close proximity to the active site for subsequent intramolecular reactions.
- Hooe, Shelby L.,Rheingold, Arnold L.,MacHan, Charles W.
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supporting information
p. 3232 - 3241
(2018/03/13)
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- Method of manufacturing tetrabuthyl ammonium acetate (by machine translation)
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PROBLEM TO BE SOLVED: use raw material, and the solvent through the proper selection of a simple and easy process suitable for the manufacture of solubility of cellulose tet love chill ammonium acetate. SOLUTION: and a starting material by tributylamine, tributylamine in polar aprotic organic solvent and by the reaction of halogenated butyl tetrabuthyl ammonium halide and a process for obtaining, in tetrabuthyl ammonium halide vopo and [...] by the reaction of an alkali metal hydroxide and a process for obtaining, in [...] vopo tetrabuthyl ammonium acetate and acetic acid tetrabuthyl by reaction of the process and to obtain. Selected drawing: fig. 1 (by machine translation)
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- An Investigation of (Diacetoxyiodo)arenes as Precursors for Preparing No-Carrier-Added [18F]Fluoroarenes from Cyclotron-Produced [18F]Fluoride Ion
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Treatment of (diacetoxyiodo)arenes (1a-1u) with cyclotron-produced [18F]fluoride ion rapidly affords no-carrier-added [18F]fluoroarenes (2a-2u) in useful yields and constitutes a new method for converting substituted iodoarenes into substituted [18F]fluoroarenes in just two steps.
- Haskali, Mohammad B.,Telu, Sanjay,Lee, Yong-Sok,Morse, Cheryl L.,Lu, Shuiyu,Pike, Victor W.
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p. 297 - 302
(2016/01/15)
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- Catalytic epoxidation of cis-stilbene and naphthalene by tetra-n-butylammonium hydrogen monopersulfate in the presence of manganese(III) tetraarylporphyrins and various anionic co-catalysts
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The epoxidation of cis-stilbene by n-Bu4NHSO5 was studied in the presence of two different manganese porphyrin complexes, [MnTPFPP(Cl) and MnTPP(Cl)], and various n-Bu4NX (X = OAc, F, Cl, Br, OCN, NO3, BF4). In general direct correlation was found between stereoselectivity of the epoxidation reaction and the nucleophilic properties of these anionic co-catalysts. Also epoxidation of naphthalene was carried out in high yield and good selectivity by n-Bu4NHSO 5 in the presence of MnTPFPP(Cl) in association with n-Bu 4NOAc or n-Bu4NF co-catalysts.
- Solati, Zahra,Hashemi, Majid,Keshavarzi, Ahmad,Rafiee, Ezzat
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experimental part
p. 149 - 153
(2012/07/17)
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- Rapid and highly selective epoxidation of styrene by meta-chloroperbenzoic acid catalyzed by manganese meso-tetrakis(pentafluorophenyl)porphyrin in the presence of tetrabutylammonium acetate and bromide
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Epoxidation of styrene with m-CPBA in the presence of Mn(TPFPP)Cl was improved to high yield (98-100%) and excellent selectivity (100%) by using n-Bu4NOAc or n-Bu4NBr as co-catalysts in less than 5 min. Also comparison of co-catalytic activity of n-Bu4NOAc, n-Bu 4NBr and imidazole in epoxidation of cis-stilbene and styrene was carried out at similar conditions.
- Solati, Zahra,Hashemi, Majid,Ebrahimi, Leila
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experimental part
p. 163 - 167
(2011/10/04)
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- Palladium-catalyzed heck reaction of aryl chlorides under mild conditions promoted by organic ionic bases
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An efficient Pd-catalyzed Heck reaction of aryl chlorides with olefins under mild conditions is described. High yields of products were achieved with n-Bu4N+OAc- as base. Significantly, the temperature of the Heck reaction of diverse nonactivated aryl chlorides can be lowered to 80 °C. The new reaction system can also tolerate a wider range of olefins.
- Xu, Hua-Jian,Zhao, Yong-Qiang,Zhou, Xin-Feng
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experimental part
p. 8036 - 8041
(2011/12/02)
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- POSITIVE RESIST COMPOSITION AND PATTERNING PROCESS
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A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid and (B) an acid generator. The resin (A) is a polymer comprising recurring units containing a non-leaving hydroxyl group represented by formula (1) wherein R1 is H, methyl or trifluoromethyl, X is a single bond or methylene, m is 1 or 2, and the hydroxyl group attaches to a secondary carbon atom. The composition is improved in resolution when processed by lithography.
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- Synthesis of a C3-symmetric furyl-cyclopeptide platform with anion recognition properties
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A new furyl amino acid derivative was trimerized to give a linear peptide and finally was cyclized. The newly generated cyclopeptide was subjected to a conformational study in order to be considered as a C3-symmetric platform for the ratio nal design of complex receptors. Moreover, the recognition properties towards cyanide, acetate and chloride anions were studied.
- Molina, Lidia,Moreno-Clavijo, Elena,Moreno-Vargas, Antonio J.,Carmona, Ana T.,Robina, Inmaculada
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experimental part
p. 4049 - 4055
(2010/09/10)
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- A naked eye detection of fluoride with urea receptors which have both an azo group and a nitrophenyl group as a signaling group
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Anion recognition via hydrogen-bonding interactions could be monitored with changes in UV-vis absorption spectra and in some cases easily monitored with naked eye. Urea receptors 1 and 2 connected with both an azo group and a nitrophenyl group as a signaling group for color change proved to be an efficient naked eye receptor for the fluoride ion. The anion recognition phenomena of the receptors 1 and 2 via hydrogen-bonding interactions were investigated through UV-vis absorption and 1H NMR spectra.
- Dang, Nhat Tuan,Park, Jin Joo,Jang, Soonmin,Kang, Jongmin
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body text
p. 1204 - 1208
(2010/09/10)
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- Direct observation of the ionization step in solvolysis reactions: Electrophilicity versus electrofugality of carbocations
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Rates and equilibria of the reactions of highly stabilized amino-substituted benzhydrylium ions (Ar2CH+) with carboxylate ions have been determined photometrically in acetone and acetonitrile solutions. Treatment of covalent benzhydryl carboxylates (Ar 2CH-O2CR) with aqueous acetone or acetonitrile leads to the regeneration of the colored amino-substituted benzhydrylium ions Ar 2CH+, which do not undergo subsequent reactions with the solvent. One can, therefore, directly measure the first step of SN1 reactions. The electrofugality order, i.e., the relative ionization rates of benzhydryl esters Ar2CH-O2CR with the same anionic leaving group, does not correlate with the corresponding electrophilicity order, i.e., the relative reactivities of the corresponding benzhydrylium ions Ar 2CH+ toward a common nucleophile. Thus, benzhydrylium ions which are produced with equal rates by ionization of the corresponding covalent esters may differ by more than 2 orders of magnitude in their reactivities toward nucleophiles, e.g., carboxylate ions. Variable intrinsic barriers account for the breakdown of the rate-equilibrium relationships. Complete free-energy profiles for the ionization of benzhydryl carboxylates Ar2CH-O 2CR are constructed, which demonstrate that the transition states of these ionizations are not carbocation-like. As a consequence, variation of the solvent-ionizing power Y has only a small effect on the ionization rate constant (m = 0.35 to 0.55) indicating that small values of m in the Winstein-Grunwald equation do not necessarily imply an SN2 type mechanism.
- Schaller, Heike F.,Tishkov, Alexander A.,Feng, Xinliang,Mayr, Herbert
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p. 3012 - 3022
(2008/09/20)
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- Effect of spacer geometry on oxoanion binding by bis- and tetrakis-thiourea hosts
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Hosts with thiourea groups bind anions by formation of multiple hydrogen bonds. This contribution discusses how spacers linking two or four thiourea groups affect the host affinity and selectivity. While most of the bis-thioureas bind H2PO4- preferentially, the extent of selectivity over chloride, acetate, and H2AsO4- is determined by the size of the binding cavity. A tetrakis-thiourea is shown to exhibit a unique H2AsO4- selectivity, and the discrimination of chloride is enhanced by specific solvation in dimethyl sulfoxide.
- Leung, Annie N.,Degenhardt, Dave A.,Bühlmann, Philippe
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p. 2530 - 2536
(2008/09/18)
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- Protons as the triggers to regulate hydrogen-bonding receptors
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(equation presented) The protonation of alkylamines in two novel receptors results in intramolecular host-guest associations between the resulting ammonium ions and crown ether macrocycles. These interactions result in conformational changes of the receptors and prevent them from acting as hydrogen bond complements for uracil and carboxylate guest species.
- Al-Sayah, Mohammad H.,Branda, Neil R.
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p. 881 - 884
(2007/10/03)
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- Process for the preparation of 1,3-dioxane derivatives useful in the preparation of HMG-COA reductase inhibitors
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A novel, overall process for the preparation of a compound of the formula I: STR1 where R1 and R2 are each independently hydrogen, an alkyl group, a cycloalkyl group, an aryl group or, taken together with the carbon atom to which they are attached, form a cycloalkyl group; and R3 is hydrogen, an alkyl group, or an aryl group, or salts thereof, useful as intermediates in the preparation of HMG-CoA reductase inhibitors; novel methods within the overall process; and novel intermediates produced by those methods.
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- Preparation and Vibrational Spectra of 13C and 18O Labelled trans-Dioxotetracyanoosmate(VI), (2-)
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Through careful acidification of the aqueous solution of (2-) in the presence of CN(-) or (13)CN(-) with acetic acid, (2-) or (2-) are formed, respectively.The reaction of Os(18)O4 and tetrabutylammonium cyanide with glacial acetic acid in anhydrous methanol yields (2-).The shifts of the infrared and Raman bands of the isotopically labelled complexes are in good agreement with Teller-Redlich calculations.The degenerate E modes, expected for tetragonal symmetry, are split by approx. 15 cm-1, indicating an orthorhombic distortion of the complex ion in the solid state.Therefore, all the observed IR- and Raman frequences are assigned according to point group D2h.For the complex containing an (16)O=Os=(18)O axis, the symmetry is lowered to C2v, and the rule of mutual exclusion is restricted.This results in a weak absorption in the infrared spectrum of the Raman active symmetric OsO stretching vibration and vice versa a weak band in the Raman spectrum for the antisymmetric infrared active mode. - Keywords: trans-Dioxotetracyanoosmate(VI), Isotopic Labeling, IR Spectra, Raman Spectra
- Preetz, W.,Sartori, C.
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